Another thing that i am concerned about is a way how to plug-in your forum to an
existing Cat application. For example i have my own user infrastructure and
registration, banning, blocking system (some things are borrowed from your code
;-)...

I must admit that FromSub::Hash is not good enough. but it doesn't hit database every request for $c->user. Store::DBIC is nice yet our Model/User.pm sub get is returning a cached user hash. so we use FromSub::Hash.